The Biogeochemistry Core will support geochemical and microbiological measurements on behalf of earth[unreadable] science and environmental engineering Projects 5, 6, and 7 and groundwater analyses for constituents of[unreadable] potential health concern for biomedical Projects 3 and 4. Using a VG Axiom (magnetic sector) High-[unreadable] Resolution Inductively Coupled Plasma-Mass Spectrometer (HR ICP-MS) housed at Lamont-Doherty[unreadable] Observatory, approximately 10,000 samples of groundwater and sediment digests will be analyzed for up to 33 major and[unreadable] trace elements. Existing methods will be refined to determine As concentrations and speciation in the field[unreadable] and in the laboratory. Sediment deposition rates will be determined over a range of time scales using the[unreadable] radioisotopes 14C, 137Cs, and 210Pb.[unreadable] Through collaboration with Dartmouth College and the Universite Paul Cezanne (France), the[unreadable] Biogeochemistry Core will support the spectroscopic characterization of Fe and As mineralogy and[unreadable] speciation for selected sediment samples at various synchrotron facilities. This will include bulk analysis by[unreadable] X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray Absorption Fine-Structure (EXAFS)[unreadable] spectroscopy, as well microbeam X-ray microprobe analysis to determine spatial heterogeneity.[unreadable] The Biogeochemistry Core will also support a concerted effort to identify the microorganisms responsible for[unreadable] mobilizing As in groundwater. This work will be conducted on the Columbia Health Sciences campus and in[unreadable] collaboration with Duquesne University. Using both culture-based on non-culture-based methods, the[unreadable] presence of arsenic-metabolizing bacteria will be determined in selected aquifer material from the U.S. and[unreadable] Bangladesh. The microbial diversity of groundwater and sediment samples will be established using[unreadable] 16srRNA and specific genes, such as the Arr and Ars operon. DMA and RNA Stable Isotope-Probing[unreadable] methods will also be developed.